Heavy metal ions contain highly toxic and non-biodegradable wastewater pollutants seriously contaminating the environment and affecting human health. Removal of heavy metal ions from the environment is a vital step towards the elimination of water pollution on a global scale. Therefore, in this study, cellulose was modified with L-cysteine, sodium alginate and polyethyleneimine to produce cellulose/sodium alginate /polyethyleneimine/L-cysteine composite hydrogel microspheres (WCMs/SA/PEI/L-Cys) in order to efficiently adsorb heavy metal ions. Co(II) and Ni(II) are successfully removed from water. After their production, the sorbents underwent examination using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and Scanning electron microscopy (SEM). In addition, the investigation of the mechanism and adsorption characteristics of cellulose-modified gel microspheres WCMs/SA/PEI/L-Cys has been completed. The majority of the adsorption of contaminants by cellulose-modified gel microspheres WCMs/SA/PEI/L-Cys adhered to the Langmuir isothermal adsorption model and quasi-secondary kinetic model. The intra-particle diffusion model was adopted for improving the fitting of the adsorption process in the materials. It was indicated that the internal and external diffusion acted together to eliminate the contaminants from the materials. When exploring the decontamination mechanism of the materials using XPS, it was shown that the functional groups containing nitrogen, oxygen and sulfur play a key role in removing contaminants. For Co(II) and Ni(II), the highest adsorption capacities of the sorbent were 358 and 373 mg/g, respectively. The material exhibited robust stability and recyclability based on the regeneration experiment results, remaining stable after six adsorption cycles and retaining over 80% of the initial adsorption amount.
Hanbang Liu,Liping Yang,Danhua Yuan,Guangye Liu,Jiacheng Xing,Yunpeng Xu,Zhongmin Liu
For air separation, the separation method relying on adsorbents has attracted wide attention as a low energy consumption process, and the development of O 2 -selective adsorbents is of great significance. Metal-organic frameworks with coordinatively unsaturated transition metal sites have great potential in O 2 -selective adsorption, but most of them cannot be completely regenerated at ambient temperature or can only be effective at very low temperatures. Herein, we report two mixed-ligand metal–organic framework adsorbents [M(AIP)(BPY) 0.5 ·H 2 O] n ·2nH 2 O with coordinatively unsaturated cobalt(II) and nickel(II) sites, which can preferentially adsorb O 2 versus N 2 , and their IAST O 2 /N 2 selectivities are both significantly greater than 1 at 25 °C. These materials exhibited excellent stability and had no loss of adsorption capacities even after immersion in water for 7 days. More importantly, O 2 adsorption–desorption cycle experiments showed that these adsorbents can be completely regenerated at ambient temperature after adsorbing O 2 , and the breakthrough experiments further confirmed their dynamic O 2 /N 2 separation potential and regeneration ability. The results of theoretical calculations suggested that the interactions between adsorbents and O 2 are stronger than those of N 2 , and they have relatively obvious differences in the N 2 and O 2 interaction energies. This work provides inspirations for searching for metal–organic frameworks that can selectively adsorb O 2 at ambient temperature.
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